Orestes (Greek: Ὀρέστης) is a tragedy by Euripides, first produced in Athens in 408 BC. Based on similar legendary material to Aeschylus' Oresteia, it recounts the flight of Orestes and Electra from the vengeance of the Furies after killing their mother Clytemnestra, the intervention of their uncle Menelaus, and the resolution of matters by the god Apollo.
Free online texts
Gutenberg: Ορέστης, Greek text. Multiple formats.
Gutenberg: The Tragedies of Euripides, Vol I, translated by Theodore Alois Buckley (1892). Multiple formats.
Internet Archive: The Plays of Euripides, v.II: Andromache, Electra, The Bacchantes, Hecuba, Heracles mad, The Phoenician Maidens, Orestes, Iphigenia among the Tauri, Iphigenia at Aulis, The Cyclops. English translation by E.P. Coleridge. Multiple formats.
Internet Classics Archive: Orestes, translated by E.P. Coleridge. HTML and TXT formats.
Poetry in Translation: Orestes, translated by George Theodoridis. Multiple formats.
University of Adelaide (Internet Archive): Orestes, translated by E.P. Coleridge.
Gutenberg: Euripides and His Age, by Gilbert Murray.
History of Ancient Greece: Euripides at War, podcast by Ryan Stitt.
Librivox: Orestes, public domain audiobook.
Wikipedia: Orestes (play)
The Great Conversation: Further reading at Tom's Learning Notes
Aeschylus: The Libation Bearers.
Aeschylus: The Eumenides.
A.E. Haigh: The Tragic Drama of the Greeks (1896).
Ancient Greek resources: Learn to read Greek classics in the original.
Bloom's Western Canon: Orestes is listed.